FIG. 1 depicts a schematic diagram of a portion of wireless communication system 100 in the prior art. Wireless communication system 100 comprises wireless terminals 101-1 through 101-6, all communicating with each other by using one or more air interfaces in the same, shared frequency band. As an example, IEEE 802.11 (i.e., “802.11”) wireless terminals 101-1, 101-2, and 101-4 communicate using an 802.11 air interface, Bluetooth wireless terminals 101-5 and 101-6 communicate using a Bluetooth air interface, and 802.11/Bluetooth wireless terminal 101-3 communicates using either an 802.11 or a Bluetooth air interface.
As depicted in FIG. 1, wireless terminal 101-2 is transmitting a signal with wireless terminal 101-3 as the intended recipient. Also, wireless terminal 101-6 is transmitting a signal with wireless terminal 101-5 as the intended recipient. Wireless terminals 101-2 and 101-6 can transmit simultaneously, although in order to do so, either (1) their respective transmissions have to be coordinated, or (2) wireless terminals 101-2 and 101-6 have to be situated far enough apart from each other to minimize interference. If, however, a wireless terminal supports two air interface protocols (e.g., wireless terminal 101-3, etc.), a mechanism must exist to prevent interference (i.e., the effect of two radios transmitting simultaneously in the same frequency band), since spatial separation of two air interfaces within the same wireless terminal is not an option.
In accordance with a first technique in the prior art, FIG. 2 depicts a block diagram of the salient components of wireless terminal 101-3. Wireless terminal 101-3 comprises host 201, A/B switch 202, 802.11 radio 203, Bluetooth radio 204, antenna switch 205, and antenna 206. Host 201 comprises a microprocessor. At any given time, host 201 communicates with 802.11 radio 203 or Bluetooth radio 204, not both, by means of A/B switch 202. 802.11 radio 203 communicates in accordance with the 802.11 air interface, and Bluetooth radio 204 communicates in accordance with the Bluetooth air interface. Antenna switch 205 directs a signal to be transmitted to antenna 206 from either 802.11 radio 203 or Bluetooth radio 204. Antenna switch 205 also directs a received signal from antenna 206 to either 802.11 radio 203 or Bluetooth radio 204. Antenna switch 205 is coordinated with A/B switch 202.
The first technique in the prior art controls contention for the shared frequency band through A/B switch 202. In addition to providing contention-free access to the shared frequency band, the first technique provides a low-cost solution. As a disadvantage, however, the air interface in use must remain in either 802.11 or Bluetooth mode for relatively long periods of time. Also, contention resolution requires manual intervention on the part of a user whenever wireless terminal 101-3 has to make a transmission over the air interface that is not presently active. Finally, the inactive air interface might miss a transmission by some other wireless terminal.
In accordance with a second technique in the prior art, FIG. 3 depicts a block diagram of wireless terminal 101-3. Wireless terminal 101-3 comprises host 301, 802.11 radio 302, Bluetooth radio 303, antenna switch 304, and antenna 305. Host 301 comprises a microprocessor. At any given time, host 301 communicates with 802.11 radio 302 or Bluetooth radio 303, but not both, by means of an internal switch. Typically, the internal switch requires the user of wireless terminal 101-3 to select the air interface to be used (e.g., from a menu, etc.). Alternatively, host 301 chooses between the air interfaces based on the type of communication it needs to send or expects to receive. 802.11 radio 302 communicates in accordance with the 802.11 air interface, and Bluetooth radio 303 communicates in accordance with the Bluetooth air interface. Antenna switch 304 directs a signal to be transmitted to antenna 305 from either 802.11 radio 302 or Bluetooth radio 303. Antenna switch 304 also directs a received signal from antenna 305 to either 802.11 radio 302 or Bluetooth radio 303. Antenna switch 304 is coordinated with the selection of the air interface.
The second technique in the prior art integrates the switch into host 301, so the intervention by the user is more convenient, even though the intervention is still possibly manual. In addition to providing contention-free access to the shared frequency band, the second technique provides a more convenient way of allowing the user to change between air interfaces. As a disadvantage, however, the air interface in use must remain in either 802.11 or Bluetooth mode for relatively long periods of time. Also, contention resolution still possibly requires manual intervention on the part of a user whenever wireless terminal 101-3 has to make a transmission over the air interface that is not presently active. Finally, the inactive air interface might miss a transmission by some other wireless terminal.
In accordance with a third technique in the prior art, FIG. 4 depicts a block diagram of wireless terminal 101-3. Wireless terminal 101-3 comprises host 401, 802.11/Bluetooth radio 402, antenna switch 403, and antenna 404. Host 401 comprises a microprocessor. Host 401 maintains an interface with the 802.11 part of 802.11/Bluetooth radio 402 and an interface with the Bluetooth part of 802.11/Bluetooth radio 402. 802.11/Bluetooth radio 402 is a single integrated circuit that communicates in accordance with the 802.11 air interface and with the Bluetooth air interface. 802.11/Bluetooth radio 402 coordinates transmissions to some extent between its 802.11 part and its Bluetooth part. Antenna switch 403 directs a signal to antenna 404 to be transmitted from either the 802.11 part of 802.11/Bluetooth radio 402 or the Bluetooth part of 802.11/Bluetooth radio 402. Antenna switch 403 also directs a received signal from antenna 404 to either the 802.11 part of 802.11/Bluetooth radio 402 or the Bluetooth part of 802.11/Bluetooth radio 402.
In the prior art, approaches of integrating and dynamically coordinating multiple wireless protocols on a single platform have focused on integration into a single integrated circuit. This control necessitates coordinating the contention for the same frequency band between the two air interfaces. If the two air interface protocols are 802.11 and Bluetooth, the control must be imposed on the two air interfaces, since there is no standardized interoperability between the two air interface protocols. When the individual wireless technologies, however, are on a rapid evolutionary path, “same chip” integration can increase cost and can cause the integrated circuit development to lag behind that of separate circuits. Also, the market demand for a dual-interface solution within a single integrated circuit can be considerably smaller than the demand for either integrated circuit supporting a single protocol only (i.e., 802.11 or Bluetooth, but not both). Furthermore, even same chip integration by itself does not inherently guarantee a tight, efficient contention control between the two air interfaces.
Therefore, the need exists for multiple radios supporting different air interface protocols, possibly on separate integrated circuits, to coordinate the use of a shared frequency band.